Some dependency fixups, removing non-devel version of libva and
adding libglvnd as a build dependency too.
libglvnd has to exist in both types of dependencies as the source
explicitly checks for its presence in build time as "runtime dependency".
Required with the proprietary drivers if KDE is in use and Spectacle
is desired to be used.
Do NOT make this a hard dependency for Spectacle since it conflicts
with the default vdpau-video.